I started to use 4-stroke Auto-Moto engines for aircraft in early 90-th. These engines have never been “alternative” for me. Many people interpret that to mean weird, more complicated or lesser way for builders who cannot afford to buy “good & proven Rotax 912S". I never considered them only as "cheap" way of aircraft engine development. Automotive companies spent hundreds of million dollars for their new engines. We all know about serious competition in this industry for the last decades. As a result, even being less expensive because of mass production, modern auto engine is way more advanced. It is a pleasure for me to design new conversion systems and fly them.
There is a lot of experience in converting of Subaru, Honda, Chevy, Nissan, Kawasaki, BMW and other engines but light and small GEO-Suzuki G10, G13 and G16 are the most interesting engines for me as Weight-Shift control aircraft (trike) designer, builder and pilot. G10 with stock fuel injection has about the same HP as popular Rotax 582 model. Trikes with G10 have good flight performances with significantly lower flight hour cost. G10 Turbo, G13BA and G16B have about the same power as Rotax 912, 912S and 914. But my favourite engine for trikes for the last several years is G13BB. Different trikes were built and supplied to customers with these engines. I test fly every one by myself. Years and hundreds of flying hours without major problems.
The GEO-Suzuki has its advantages, as does the Rotax 912. My opinion as an aviation engineer and pilot, and the opinion of many builders and pilots who have tried both Air Trikes conversions and 912 engines is that our GEO-Suzuki conversion in many aspects is the preferable choice.

I started to use 4-stroke Auto-Moto engines for aircraft in early 90-th. These engines have never been “alternative” for me. Many people interpret that to mean weird, more complicated or lesser way for builders who cannot afford to buy “good & proven Rotax 912S". I never considered them only as "cheap" way of aircraft engine development. Automotive companies spent hundreds of million dollars for their new engines. We all know about serious competition in this industry for the last decades. As a result, even being less expensive because of mass production, modern auto engine is way more advanced. It is a pleasure for me to design new conversion systems and fly them.
There is a lot of experience in converting of Subaru, Honda, Chevy, Nissan, Kawasaki, BMW and other engines but light and small GEO-Suzuki G10, G13 and G16 are the most interesting engines for me as Weight-Shift control aircraft (trike) designer, builder and pilot. G10 with stock fuel injection has about the same HP as popular Rotax 582 model. Trikes with G10 have good flight performances with significantly lower flight hour cost. G10 Turbo, G13BA and G16B have about the same power as Rotax 912, 912S and 914. But my favourite engine for trikes for the last several years is G13BB. Different trikes were built and supplied to customers with these engines. I test fly every one by myself. Years and hundreds of flying hours without major problems.
The GEO-Suzuki has its advantages, as does the Rotax 912. My opinion as an aviation engineer and pilot, and the opinion of many builders and pilots who have tried both Air Trikes conversions and 912 engines is that our GEO-Suzuki conversion in many aspects is the preferable choice.